Structurally Conserved Aromaticity of Tyr249 and Phe264 in Helix 7 Is Important for Toxicity of the Bacillus thuringiensis Cry4Ba Toxin
| Autor: | Chanan Angsuthanasombat, Kasorn Tiewsiri |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Models
Molecular Circular dichroism Phenylalanine Bacterial Toxins Molecular Sequence Data Mutant Bacillus thuringiensis Biology Crystallography X-Ray medicine.disease_cause Hydrocarbons Aromatic Biochemistry Protein Structure Secondary Hemolysin Proteins Structure-Activity Relationship Protein structure Bacterial Proteins medicine Animals Amino Acid Sequence Molecular Biology Escherichia coli Alanine Bacillus thuringiensis Toxins Toxin Circular Dichroism General Medicine biology.organism_classification Endotoxins Culicidae Structural Homology Protein Larva Tyrosine Mutant Proteins Protein Processing Post-Translational Delta endotoxin |
| Zdroj: | BMB Reports. 40:163-171 |
| ISSN: | 1976-6696 |
| DOI: | 10.5483/bmbrep.2007.40.2.163 |
| Popis: | Functional elements of the conserved helix 7 in the poreforming domain of the Bacillus thuringiensis Cry delta- endotoxins have not yet been clearly identified. Here, we initially performed alanine substitutions of four highly conserved aromatic residues, Trp(243), Phe(246), Tyr(249) and Phe(264), in helix 7 of the Cry4Ba mosquito-larvicidal protein. All mutant toxins were overexpressed in Escherichia coli as 130-kDa protoxins at levels comparable to the wild-type. Bioassays against Stegomyia aegypti mosquito larvae revealed that only W243A, Y249A or F264A mutant toxins displayed a dramatic decrease in toxicity. Further mutagenic analysis showed that replacements with an aromatic residue particularly at Tyr(249) and Phe(264) still retained the high-level toxin activity. In addition, a nearly complete loss in larvicidal activity was found for Y249L/F264L or F264A/ Y249A double mutants, confirming the involvement in toxicity of both aromatic residues which face towards the same direction. Furthermore, the Y249L/F264L mutant was found to be structurally stable upon toxin solubilisation and trypsin digestion, albeit a small change in the circular dichroism spectrum. Altogether, the present study provides for the first time an insight into the highly conserved aromaticity of Tyr(249) and Phe(264) within helix 7 playing an important role in larvicidal activity of the Cry4Ba toxin. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|